Manufacture of photographic gelatin emulsions



Patented as, 1939 UNITED STATE mursc'ruas or moroonarmc camrm mansions IEmil Joachim Bil-r, Bltterleld, and Hans ma.

and Gustav Wilmanns, Wolien, Kreis Bitterield, Germalmanignors to AsiaAnsco Corporation. Binghamton, N. Y., a corporation of New York NoDrawing.

I Our present invention relates to the manulecture of photographicgelatin emulsions.

One of its objects is to provide an improved photographic gelatinemulsion free from log.

Further objects will be seen from the detailed specification iollowinghereafter.

It is known that some kinds of gelatin are not useful for the production01' photographic emulsions owing to the fact that in the course of theusual process for producing the emulsion the emulsion suflers anextensive foggin which is apparently due to the presence in the naturalgelatin 0! too high a proportion of substances which promote ripening.

According to this invention a gelatin 01' this kind can be renderedsuitable for use for the productionof photographic emulsions with goodresults, by adding to the gelatin or'to the emulsion at. any desiredstage in the preparation of the gelatin or emulsion, an amino-purinesuch as guanine or adenine, or mixtures oi these compounds. By theaddition of one or these substances the tendency towards fogging, is sostrongly diminished that gelatin of this kind can be worked up intoemulsions of all kinds in the same manner as a photographic gelatin oithe highest grade. The compounds are added in the term or solutions.Suitable solvents are water and alcohols and may be made alkaline by theaddition of a small quantity of caustic soda.

The proportion of the substance to be added is adjusted according to theextent to which the gelatin or emulsion undergoes i ss ns. previouslydeterminedintheusualmannsr. V J

Application July 10, 1935, Serial In Germany Ill! 14, 1934 The followingexamples illustrate the invention:

Example 1.-To a gelatin having a strong tendency to iog there is added asolution oi! 10 millirams of guanine in a mixture of 10 cc. 0! water and2 cc. of

n T6 NGOH n vNaOH on 1 kilo of dry gelatin;

What we claim is:

1. A photographic silver halide gelatin emu-- sion containing aminopurines in an amount oi about lo milligrams per kilo oi dry gelatin.

' 2. A. photographic silver halide gelatin emulsion containing guaninein an amount oi about 10 milligrams per kilo of dry gelatin.

3. A photographic silver. halide gelatineontalningamixtureoiguanineandadenineinln,

amount or aboutlomilligramsperkilooidry gelatin.

I. J. ma.

HANS ERICK.

-. cos-ray wnamma

